1. Field of the Invention
The present invention relates to a filter material take-up product for an air filter. More particularly, the invention relates to a filter material take-up product for an air filter, which is used for a clean room, a clean bench or the like for a semiconductor, a liquid crystal or a bio/food industry, or an air filter for a building air conditioner, an air cleaner etc.
2. Description of the Related Art
A filter material for a high-efficiency particulate air (HEPA) filter, a filter material for an ultra low penetration air (ULPA) filter, and a filter material for an ASHRAE air filter, which are mainly made of a glass fiber, are used in various fields such as a clean room or a clean bench for a semiconductor, a liquid crystal or a bio/food industry, or an air filter for a building air conditioner, an air cleaner etc.
In connection with an increasing integration degree of LSI, there has been a major issue in a semiconductor manufacturing process in recent years: The issue is that a very small amount of a gas component (hereinafter referred to as an outgas) of a ng/m3 order generated from the air filter and other components which constitute a clean room is stuck to a silicon wafer or a glass substrate, causing a reduction in yield of semiconductor products.
The outgas components which are considered problematic here mean organic substances in general that stick to the silicon wafer easily, and it is said that a polar substance sticks to the silicon wafer particularly easily.
Aside from the above, a recent environmental hormone problem, and a health hazard problem such as an allergy due to a volatile organic matter, represented by a sick building syndrome, have come under close scrutiny. Thus, there has been a need to heed the outgas from the air filter used for a building air conditioner or an air cleaner. Among carboxylate esters, di-2-ethylhexyl phthalate (DOP) and di-n-butyl phthalate (DBP) that are a phthalate ester, are particularly known as environmental hormones, and are substances to be controlled. As for a filter material for an air filter that solves this problem, a proposal has been made to limit a raw material used for a filter material in WO 97/04851, and Japanese Patent Laid-Open Heisei 10 (1998)-244112 etc.
On the other hand, the filter material for the air filter is continuously processed when pleating is carried out in a filter-processing maker. Thus, when shipped from a manufacturing factory of the filter material for the air filter, the filter is wound on a winding core made of paper, a synthetic resin, a metal or the like to be made in a shape of a take-up roll product. A packing method employed is wrapping the take-up roll by a film for the purpose of preventing it from being wet due to water, i.e., moisture prevention, as well as prevention of dusts and chips, while being transported or stored, and housing it in an outer box made of a cardboard or the like.
Regarding a packing method of an air filter unit, Japanese Patent Laid-Open Heisei 11 (1999)-253715 discloses a packing method by which an air filter is packed in a space where no gaseous organic matters exist, using a packing material which generates no gaseous organic matters. This publication describes that if the air filter, in which a gaseous organic matter is adsorbed on a filter material thereof through the assembling environment and the packing material, is directly installed in a clean room, the gaseous organic matter is radiated within the clean room and contaminates the air for at least 6-month storage period after the installation. However, although the publication defines a kind of a resin for a resin sheet, and a kind of a plasticizer and an antioxidant as the packing material, no consideration is given regarding influences of other additives, and there is no definition of the amount of an outgas from the packing material. Besides, there is no mention of importance of a packing method of a filter material take-up product. Actually, since the air filter takes a shape where the filter material folded in zigzags is fixed by an aluminum frame or a wooden frame, a surface of the filter material in a packed state is always in contact with or in the vicinity of the packing material, thus susceptible to the exposure of the outgas, which is a harsh condition. On the other hand, when the filter material take-up product for the air filter is packed, the condition for the filter material take-up product is totally different from the above, because only an upper winding of the roll is in contact with the packing material. Therefore, in the publication, no consideration has been given whatsoever to the packed filter material take-up product for the air filter from the standpoint of the outgas.